1. Field of Invention
The present invention relates to a stagger sensor and method for improving modulation transfer function. More particularly, the present invention relates to a stagger sensor and method for improving scanning resolution of a scanner.
2. Description of Related Art
Photocopiers, fax machines and scanners are common devices for capturing and converting images into electronic data for ease of printing, storage, transmission or image conversion. In general, optical sensors such as charge-coupled device (CCD) or contact image sensor (CIS) are used to extract image information. To capture a color image, the optical sensor normally consists of an array of CCD each capable of sensing at least the three primary colors red, green and blue. In a normal operation, all the CCD elements in the array are exposed to light for a predefined period. The amount of electric charge accumulated after the exposure is transferred to analogue shift registers for subsequent processing.
To enhance the resolution along the X-axis (long axis of the optical sensor), points are inserted along the X-axis so that data having an optical resolution greater than the optical sensor can be obtained. However, size of the cells within the optical sensor cannot be changed. Hence, brightness level data captured by the optical sensor during a scanning operation, if each sensing cell uses a resolution greater than the resolution of the optical sensor, is the average brightness level of several pixels. Therefore, using such a method to increase resolution may lower the performance of modulation transfer function (MTF).